In a conventional carburetion system for an automotive engine, gasoline and air are drawn into a carburetor and are mixed in appropriate proportions for delivery to the engine. In this arrangement, it is desirable that the gasoline fuel be fully vaporized and mixed with the air to assure maximum fuel efficiency and to avoid release of unburned hydrocarbon pollutants to the atmosphere in the engine exhaust. However, particularly where operation of the engine is initiated from a cold start under low ambient temperature conditions, it is difficult to achieve full fuel vaporization in a conventional carburetion system. That is, where the temperature of the air and fuel drawn into the carburetor is low, and where the engine itself is also at a low temperature, full fuel vaporization does not always occur and the air-fuel mixture delivered to the engine tends to include droplets of unvaporized fuel. In this regard, conventional carburetors are adapted to provide a fuel rich air-fuel mixture under such operating conditions to facilitate motor starting and this results in incorporation of even greater amounts of unvaporized fuel in the air-fuel mixture. Attempts have been made to preheat the air-fuel mixture delivered to an automotive engine, but these attempts have not been fully effective in transferring heat to the air-fuel mixture and have not usually been fully operative sometime often after initiation of engine operation.
It is an object of this invention to provide a novel and improved carburetion system for an automotive engine; to provide such an improved carburetion system which achieves improved vaporization and mixing of fuel with air for delivery to an automotive engine; to provide such an improved system which efficiently and effectively heats an air-fuel mixture for achieving improved fuel vaporization prior to delivery of the air-fuel mixture to the engine; to provide such a system which is operative to heat the air-fuel mixture almost immediately after initiation of engine operation and to provide such an improved carburetion system which is easily and economically manufactured and which is adapted for use with conventional automotive engines.
Briefly described, the novel and improved carburetion system of this invention includes a carburetor of any conventional type having an air-fuel passage, having an air inlet to the air fuel passage, having a fuel inlet to the air-fuel passage for mixing fuel with air in the air-fuel passage, and an outlet from the air-fuel passage for delivering a mixture of air and vaporized fuel to an automotive engine. The improved carburetion system of this invention then further includes a heater means preferably comprising a body of ceramic resistor material of positive temperature coefficient of resistivity which is adapted to display a sharp, anomalous increase in resistivity when the body is heated to a selected temperature. The resistor body is provided with a plurality of passages extending through the body between opposite ends of the body and means are provided for directing electrical current through the body for heating the body. The heater means is then mounted relative to the carburetor so that at least part of at least one constituent of the air-fuel mixture is passed through the heater passages in heat-transfer relation to the heater body for facilitating vaporization of the fuel constituent of the air-fuel mixture. Preferably, for example, the heater means is mounted on the carburetor at the outlet of the air-fuel passage with the heater passages aligned with the air-fuel passage so that the air-fuel mixture provided by the carburetor is directed through the heater passages in efficient heat-transfer relation to the heater body. In this way, highly effective vaporization of the fuel in the air-fuel mixture is achieved prior to delivery of the air-fuel mixture to the engine. Alternately, the heater means is disposed in the air inlet to the air-fuel passage or in the fuel inlet to the air-fuel passage for permitting the air or fuel to pass through the heater body passages in heat-transfer relation to the heater body.
In a preferred embodiment of this invention, where the heater means is mounted at the outlet of the air-fuel passage for passing the air-fuel mixture through the heater passages, a screen mesh is mounted at the inlet side of the heater passages for dispersing fuel droplets in the air-fuel mixture to assure that the droplets are fully vaporized in passing through the heater passages. Preferably also, a screen mesh is mounted at the outlet side of the heater body passages to prevent any chips of the ceramic resistor body falling into the automotive engine. In a preferred embodiment of the invention, the heater body is provided with contacts in ohmic contact relation to the ceramic resistor body, the heater body is enclosed in a housing having apertures aligned with the heater body passages, and terminal means are connected to the ohmic contacts to extend exteriorly of the housing. The housing is then provided with means for mounting the housing at the outlet of the air-fuel passage of the carburetor sealed to the carburetor with the housing apertures and the heater body passages aligned with the air-fuel passage.